Microstructure-sensitive probabilistic modeling of HCF crack initiation and early crack growth in Ni-base superalloy IN100 notched components

Microstructure-sensitive simulation-based strategies for modeling fatigue life reduction in cyclically loaded notched components offer a means to augment costly experiments and to project performance of microstructures not yet processed. To advance design tools for notch fatigue resistance in aircraft gas turbine engine components, we present a formulation that links microstructure heterogeneity (grain size distribution) to size effects and fatigue scatter in notched polycrystalline Ni-base superalloy IN100 specimens. Simulated double-edged notched specimens with various notch radii are subjected to completely-reversed, quasistatic, isothermal (650 degrees C), strain-controlled loading at three different strain amplitudes. Polycrystal plasticity and experimentally-calibrated crack formation/growth laws are used to correlate cyclic plastic slip to the probability of forming and propagating a crack from grain scale to a transition crack length at which LEFM is applicable. Probabilistic strain-life and cumulative distribution function (CDF) plots show that larger notch sizes display a larger notch size effect and fatigue knockdown effect. The proposed CDF can be determined for any failure probability and number of cycles, which has implications for minimum fatigue life design of aircraft gas turbine engine components. (C) 2011 Elsevier Ltd. All rights reserved.